Often, individuals choose placement of tattoos so that the tattoos can be concealed by dress or formal wear.
However, tattooed individuals in colder climates often conceal their tattoos as a side effect of wearing heavy clothing and would like to continue to display their tattoos.
Enter the tattoo
window. Tattoo windows are translucent plastic windows embedded in sweaters, long sleeve shirts, or other pieces of outerwear that allow viewing of tattoos or other body modifications. Generic long sleeve shirts or sweaters and coats might have arm and shoulder windows to cover some of the more popular spots, or the individual could customize window placement.
Velcro swatches of cloth might be used to expose or cover the window as is appropriate or desirable. A window cover would also mitigate the loss of body heat in particularly chilly climates, as the average translucent plastic does not have appreciable insulation properties.
People who might stand to benefit from this technology: mall Santas, astronauts, and those who enjoy 19th century beach attire.
Addendum: The concept at work here might be described as selective nudity.